Differential device

Abstract

To provide a differential arrangement which inhibits complication of a cast while enabling an oil hole for supplying a lubrication oil to the interior of a differential case to be formed by casting to improve mass productivity.SOLUTION: A differential arrangement 1 includes: a differential case 2 integrally having a cylindrical part 21 and a bottom part 23; a first side gear 31 and a second side gear 32 disposed within the differential case 2; and a pinion gear set 4 formed by causing a first pinion gear 41 which engages with the first side gear 31 and a second pinion gear 42 which engages with the second side gear 32 to engage with each other. In the differential case 2, an oil hole 20 for introducing a lubrication oil is formed extending in an axial direction. One axial end 201 of the oil hole 20 is formed at the cylindrical part 21 and the other axial end 202 of the oil hole 20 is open on an outer surface 23a of the bottom part 23. A width W of the oil hole 20 in a circumferential direction of the cylindrical part 21 is formed so as not to narrow from the one end 201 to the other end 202.SELECTED DRAWING: Figure 2

Description

Technical Field

[0005] ,

[0001] The present invention relates to a differential device that distributes an input driving force to a pair of drive shafts while allowing differential.

Background Art

[0002] Conventionally, as a differential device for a vehicle, there is one including a differential case that rotates receiving the driving force of a drive source, a first side gear and a second side gear disposed in the differential case along the rotation axis of the differential case, and a plurality of pinion gear sets formed by meshing a first pinion gear meshing with the first side gear and a second pinion gear meshing with the second side gear. The applicant of the present application has proposed the one described in Patent Document 1 as such a differential device.

[0003] In the differential device described in Patent Document 1, two second pinion gears are meshed with one first pinion gear to constitute a set of pinion gear sets. The first pinion gear is formed longer than the second pinion gear. In the cylindrical portion of the differential case (the first housing member), a plurality of bores for respectively accommodating a plurality of pinion gear sets and a plurality of recesses for introducing lubricating oil into the differential case are formed. The recesses are formed, for example, by cutting in a portion corresponding to the outer periphery of the first side gear and penetrate between the inner and outer peripheral surfaces of the cylindrical portion of the differential case.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0034] -

[0036] and FIG. 1)

Summary of the Invention

Problems to be Solved by the Invention

[0005] The differential described in Patent Document 1 had the problem that the processing time required to form multiple recesses by cutting was long, which reduced mass productivity. Furthermore, if the recesses were to be formed by casting, it would be necessary to combine three or more molds, including two outer molds that are divided axially before and after the recesses to form the outer shape of the differential case, and an inner mold for forming the inner shape of the differential case, which would complicate the structure of the mold.

[0006] Therefore, the present invention aims to provide a differential that enables the formation of oil holes for supplying lubricating oil within the differential case by casting, while suppressing the complexity of the mold, thereby improving mass production efficiency. [Means for solving the problem]

[0007] To achieve the above objective, the present invention comprises a differential case that rotates in response to the driving force of a drive source, a first side gear and a second side gear coaxially arranged within the differential case along the rotation axis of the differential case, and a plurality of pinion gear sets formed by meshing a first pinion gear that meshes with the first side gear and a second pinion gear that meshes with the second side gear, wherein the differential case has a cylindrical portion with a plurality of housing holes formed therein for housing each of the plurality of pinion gear sets, and the cylindrical portion The differential case integrally comprises a flange portion provided on the outer circumference of one end and a bottom portion provided on the inside of the other end of the cylindrical portion, and an oil hole for introducing lubricating oil into the differential case is formed in the differential case extending in the axial direction along the axis of rotation, with one end of the oil hole in the axial direction formed in the cylindrical portion and the other end in the axial direction open to the outer surface of the bottom portion, and the width of the oil hole in the circumferential direction of the cylindrical portion is formed so as not to narrow from one end to the other end. Ori , The minimum distance between the inner surface of the oil hole at the bottom and the axis of rotation is shorter than half the diameter of the tip circle of the first side gear. A differential device is provided. [Effects of the Invention]

[0008] According to the differential gear of the present invention, oil holes for supplying lubricating oil to the differential case can be formed by casting, thereby improving mass production efficiency. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view showing a differential according to an embodiment of the present invention, arranged within a case member fixed to the vehicle body. [Figure 2] This is a perspective view showing the differential gear; (a) shows the overall appearance of the gear, and (b) shows the interior with a portion of the differential case cut open. [Figure 3] This is an external view of the differential gear as seen along the rotation axis. [Figure 4] Figure 1 is a cross-sectional view of the differential on line AA. [Figure 5] (a) to (c) are explanatory diagrams showing the sand mold forming process. [Figure 6] (a) to (c) are explanatory diagrams showing the casting process. [Modes for carrying out the invention]

[0010] [Embodiment] Embodiments of the present invention will be described with reference to the drawings. The embodiments described below are shown as preferred specific examples for carrying out the present invention, and some parts specifically illustrate various technically preferable technical matters, but the technical scope of the present invention is not limited to these specific embodiments.

[0011] (Overall configuration of the differential unit) Figure 1 is a cross-sectional view showing a differential according to an embodiment of the present invention, arranged within a case member fixed to the vehicle body. Figure 2 is a perspective view of the differential, where (a) shows the overall appearance of the device, and (b) shows the interior with a portion of the differential case cut away. Figure 3 is an external view of the differential along its rotation axis. Figure 4 is a cross-sectional view of the differential along line AA in Figure 1. In Figure 1, the cross-section of the differential along line BB shown in Figure 4 is shown.

[0012] This differential 1 is mounted on a vehicle and used to distribute the input driving force to a pair of drive shafts with differential action. In this embodiment, as an example, the case in which the differential 1 is used to distribute the driving force of a drive source such as an engine or electric motor to drive shafts connected to the left and right wheels with differential action is described. However, it is also possible to mount the differential 1 on a four-wheel drive vehicle and use it as a center differential to distribute driving force to the front and rear propeller shafts, which act as drive shafts.

[0013] The differential gear 1 is housed in a case member 10 fixed to the vehicle body and is supported by a first tapered roller bearing 11 and a second tapered roller bearing 12, and rotates about the axis of rotation O. The first tapered roller bearing 11 and the second tapered roller bearing 12 each have inner rings 111, 121, outer rings 112, 122, a plurality of partially conical rollers 113, 123 positioned between the inner rings 111, 121 and the outer rings 112, 122, and cages 114, 124 that hold the plurality of partially conical rollers 113, 123, with the outer rings 112, 122 being held by the case member 10.

[0014] In the differential gear 1, an annular ring gear 13 is fixed by multiple bolts 14, and the driving force from the drive source is input from a pinion gear shaft (not shown) that meshes with the ring gear 13, via the ring gear 13. Note that in Figure 1, one of the multiple bolts 14 is shown. In addition, lubricating oil is supplied to the differential gear 1 as oil droplets 100 from above in the vertical direction of the case member 10.

[0015] The differential device 1 includes a bottomed cylindrical differential case 2 that rotates upon receiving the driving force of a drive source, a first side gear 31 and a second side gear 32 coaxially arranged within the differential case 2 along the rotation axis O of the differential case 2, and a plurality of pinion gear sets 4 formed by meshing a first pinion gear 41 meshing with the first side gear 31 and a second pinion gear 42 meshing with the second side gear 32, and a lid member 5 that closes the opening of the differential case 2. In FIGS. 3 and 4, the rotation direction of the differential case 2 when the vehicle is moving forward is indicated by an arrow C. The rotation direction indicated by this arrow C is the main rotation direction of the differential case 2.

[0016] A tubular boss portion 51 is formed at the center of the lid member 5, and the inner ring 121 of the second tapered roller bearing 12 is fitted onto the outer periphery of this boss portion 51. A spiral oil groove 511 is formed on the inner peripheral surface 51a of the boss portion 51. The differential case 2 and the lid member 5 are fastened by a plurality of fastening bolts 15. In FIGS. 2 and 3, the shaft portions of the fastening bolts 15 are shown. The mating surface 2a of the differential case 2 that abuts against the lid member 5 is flat cut.

[0017] In the present embodiment, the differential device 1 has three sets of pinion gear sets 4. Each pinion gear set 4 is configured to have one first pinion gear 41 and two second pinion gears 42 arranged parallel to the rotation axis O. Hereinafter, the direction parallel to the rotation axis O is referred to as the axial direction, the direction perpendicular to the rotation axis O is referred to as the radial direction. Also, the direction perpendicular to the axial direction and the radial direction is referred to as the circumferential direction.

[0018] The first side gear 31, the second side gear 32, the first pinion gear 41, and the second pinion gear 42 are helical gears having helical teeth formed on their outer peripheral surfaces. As shown in FIG. 1, a spline fitting hole  310 is formed at the center of the first side gear 31, to which one of the left and right drive shafts, i.e., the drive shaft 61, is non-rotatably connected. Further, a spline fitting hole 320 is formed at the center of the second side gear 32, to which the other of the left and right drive shafts, i.e., the drive shaft 62, is non-rotatably connected.

[0019] The pitch circle diameter P1 of the first side gear 31 is formed to be larger than the pitch circle diameter P2 of the second side gear 32. A pair of center washers 16 are arranged between the first side gear 31 and the second side gear 32. The twist direction of the helical teeth of the first side gear 31 is opposite to the twist direction of the helical teeth of the second side gear 32.

[0020] The first pinion gear 41 and the second pinion gear 42 have different axial lengths, and the second pinion gear 42 is formed shorter than the first pinion gear 41. The first pinion gear 41 is arranged across the outer peripheral sides of the first side gear 31 and the second side gear 32. The second pinion gear 42 is arranged on the outer peripheral side of the second side gear 32. The first pinion gear 41 integrally has an axially one - end - side gear portion 411 meshing with the first side gear 31 and an axially other - end - side gear portion 412 meshing with two second pinion gears 42.

[0021] The axially one - end - side gear portion 411 is formed with a larger pitch circle diameter than the axially other - end - side gear portion 412. Also, the twist angle of the tooth flanks of the axially one - end - side gear portion 411 is formed larger than the twist angle of the tooth flanks of the axially other - end - side gear portion 412. Thereby, the TBR (Torque Bias Ratio) when the first side gear 31 rotates faster than the second side gear 32 and the TBR when the second side gear 32 rotates faster than the first side gear 31 are equalized.

[0022] The differential case 2 is a casting manufactured by the manufacturing method described later, and has a cylindrical cylindrical portion 21 formed with a plurality of accommodation holes 210 for respectively accommodating a plurality of pinion gear sets 4, a flange portion 22 provided on the outer periphery of one axial end portion of the cylindrical portion 21, a bottom portion 23 provided inside the other axial end portion of the cylindrical portion 21, and a tubular boss portion 24 provided to project axially from the radially inner end portion of the bottom portion 23 integrally. A spiral oil groove 241 is formed on the inner peripheral surface​​​The inner ring 111 of the first tapered roller bearing 11 is fitted onto the outer circumference of the boss portion 24. The bottom portion 23 is provided with an annular projection 231 that protrudes axially so as to surround the boss portion 24, and this annular projection 231 and the inner ring 111 of the first tapered roller bearing 11 are aligned in the axial direction. A shim for preload adjustment may be placed between the annular projection 231 and the inner ring 111 of the first tapered roller bearing 11. The annular projection 231 has a notch 231b formed so as to be recessed radially inward from its outer circumference 231a, and this notch 231b facilitates the introduction of lubricating oil between the inner ring 111 and the outer ring 112 of the first tapered roller bearing 11. In this embodiment, as shown in Figure 3, the annular projection 231 has one notch 231b, but the annular projection 231 may have multiple notches 231b.

[0024] The flange portion 22 of the differential case 2 has multiple bolt insertion holes 220 through which multiple bolts 14 for fixing the ring gear 13 are inserted. The same number of bolt insertion holes 50 are also formed in the cover member 5, and each of the multiple bolts 14 is inserted through the bolt insertion holes 220 and 50 of the flange portion 22 of the differential case 2 and the cover member 5, and screwed into the ring gear 13.

[0025] The first side gear 31 is positioned closer to the bottom 23 of the differential case 2 than the center washer 16. The second side gear 32 is positioned closer to the flange portion 22 than the center washer 16. A pair of first side washers 17 are positioned between the first side gear 31 and the bottom 23 of the differential case 2. A pair of second side washers 18 are positioned between the second side gear 32 and the cover member 5. The second pinion gear 42 is positioned offset from the bottom 23 towards the flange portion 22 in the axial direction of the cylindrical portion 21.

[0026] As shown in Figure 4, in this embodiment, three housing holes 210 are formed at equal intervals in the circumferential direction. Each housing hole 210 has a first housing portion 211 for housing the first pinion gear 41 and two second housing portions 212 for housing the two second pinion gears 42, respectively. The two second housing portions 212 are formed on both sides of the first housing portion 211 in the circumferential direction of the cylindrical portion 21 and are in communication with the first housing portion 211. The axial length of the second housing portions 212 is shorter than the axial length of the first housing portion 211. The second housing portions 212 of each pair of adjacent housing holes 210 in the circumferential direction of the cylindrical portion 21 are separated by a partition wall 213.

[0027] When the first pinion gear 41 rotates within the housing hole 210, the tooth tip surface 41a of the first pinion gear 41 slides against the inner surface 211a of the first housing portion 211. Similarly, when the second pinion gear 42 rotates within the housing hole 210, the tooth tip surface 42a of the second pinion gear 42 slides against the inner surface 212a of the second housing portion 212. The frictional force generated by these sliding movements becomes a differential limiting force that restricts the differential rotation between the first side gear 31 and the second side gear 32. As a result, even if one of the wheels slips, a driving force corresponding to the differential limiting force is transmitted to the other wheel.

[0028] (Configuration of differential case 2) The differential case 2 has an oil hole 20 extending in the axial direction for introducing lubricating oil into the differential case 2. One axial end 201 of the oil hole 20 is formed in the cylindrical portion 21, and the other axial end 202 is open to the outer surface 23a of the bottom portion 23. The outer surface 23a is the axial end face on the bottom portion 23 side of the differential case 2. The oil hole 20 is formed between the first housing portions 211 of a pair of housing holes 210 that are aligned axially with the partition wall 213 of the cylindrical portion 21 and adjacent in the circumferential direction.

[0029] The oil hole 20 has a pair of inner surfaces 20a and 20b, which face each other in the circumferential direction of the cylindrical portion 21. Of the pair of inner surfaces 20a and 20b, one inner surface 20a, which faces forward in the main rotation direction of the differential case 2, is concave, and the other inner surface 20b, which faces rear in the main rotation direction of the differential case 2, is convex.

[0030] The shapes of the inner surfaces 20a and 20b facilitate the introduction of lubricating oil from the oil holes 20 into the differential case 2. Specifically, the concave shape of one inner surface 20a prevents lubricating oil adhering to that surface from being ejected out of the oil holes 20 by the centrifugal force caused by the rotation of the differential case 2. Furthermore, the convex shape of the other inner surface 20b increases the opening area of ​​the oil holes 20 on the outer circumferential surface 21a of the cylindrical portion 21, making it easier for lubricating oil to enter the oil holes 20.

[0031] The circumferential width W (see Figure 3) of the oil hole 20 in the circumferential direction of the cylindrical portion 21 is formed so as not to narrow from one end 201 to the other end 202 of the oil hole 20. In this embodiment, the circumferential width W is constant throughout the entire axial direction of the oil hole 20, and the pair of inner surfaces 20a and 20b are parallel to the axis of rotation O. However, the oil hole 20 may be formed such that the circumferential width W of the oil hole 20 gradually widens towards the other end 202.

[0032] Furthermore, the circumferential width W of the oil hole 20 is widest near the outer circumferential surface 21a of the cylindrical portion 21, which is at the radially outer end of the oil hole 20, and becomes narrower towards the inner circumferential surface 21b of the cylindrical portion 21, which is at the radially inner end of the oil hole 20. The circumferential width W of the oil hole 20 between a pair of adjacent accommodating holes 210 in the circumferential direction is equal to the circumferential width of the partition wall 213. In this embodiment, when the cylindrical portion 21 is viewed in the axial direction, the second accommodating portion 212 of the accommodating hole 210 and the oil hole 20 do not overlap, but a part of the second accommodating portion 212 and a part of the oil hole 20 may overlap in the axial direction of the cylindrical portion 21.

[0033] As shown in Figure 3, when the bottom 23 of the differential case 2 is viewed from the axial direction, the tooth tips of the first side gear 31 protrude radially outward from the inner bottom surface 20c of the oil hole 20 in the radial direction of the differential case 2. In other words, the minimum distance Da between the oil hole 20 and the axis of rotation O at the bottom 23 of the differential case 2 is shorter than half the tooth tip circle diameter Db of the first side gear 31 (see Figure 1). This makes it easier for lubricating oil adhering to the inner bottom surface 20c of the oil hole 20 to enter the interior of the differential case 2. Furthermore, the minimum distance Da is shorter than half the inner opening diameter Dc (see Figure 1) of the end of the outer ring 112 of the first tapered roller bearing 11 on the bottom 23 side. This makes it easier for lubricating oil adhering to the inner bottom surface 20c of the oil hole 20 to enter between the inner ring 111 and the outer ring 112 of the first tapered roller bearing 11.

[0034] (Manufacturing method for differential case 2) Next, the manufacturing method of the differential case 2 will be explained with reference to Figures 5 and 6. The differential case 2 is manufactured by a sand mold forming process, a casting process, and a cutting process, in which a part of the casting obtained in the casting process is cut. In Figures 5 and 6, the left-right direction corresponds to the horizontal direction, and the up-down direction corresponds to the up and down of the vertical direction.

[0035] Figures 5(a) to 5(c) are explanatory diagrams showing the configuration and operation of a sand mold forming machine 7 used in the sand mold forming process. The sand mold forming machine 7 includes a cylindrical member 71 with a sand hopper 711 provided at its top, a fixed metal mold 72 positioned at one end of the cylindrical member 71, a metal sliding mold 73 that can move back and forth inside the cylindrical member 71, and a piston 74 that moves the sliding mold 73.

[0036] The fixed mold 72 is provided with a recess 721 for forming the outer shape of the sand mold 8 (see Figure 5(c)). The sliding mold 73 is provided with a protrusion 731 for forming the internal shape of the sand mold 8. Figures 5(a) and (b) show a cross-section of the fixed mold 72. Also, in Figures 5(a) to (c), the foundry sand 80 is shown in light gray.

[0037] In the first stage of the sand mold forming process, as shown in Figure 5(a), foundry sand 80 is injected from a sand hopper 711 into the space 710 between a fixed mold 72 positioned at one end of a cylindrical member 71 and a sliding mold 73 positioned at the other end of the cylindrical member 71. In the second stage of the sand mold forming process, as shown in Figure 5(b), the sliding mold 73 is moved toward the fixed mold 72 by a piston 74 to compress the foundry sand 80 and perform mold clamping. In the third stage of the sand mold forming process, as shown in Figure 5(c), the fixed mold 72 is retracted from the cylindrical member 71, and the sand mold 8 is pushed out of the cylindrical member 71 by the sliding mold 73.

[0038] The sand mold 8 is provided with a convex portion 81 formed by the fixed mold 72 and a recess 82 formed by the sliding mold 73. The sand mold 8 is also provided with a plurality of protrusions 83 for forming a plurality of oil holes 20 of the differential case 2, which protrude toward the center of the recess 82. These plurality of protrusions 83 are formed by recesses 731a formed in the convex portion 731 of the sliding mold 73.

[0039] Figures 6(a) to 6(c) are explanatory diagrams illustrating the casting process. In the casting process, a single casting 9 is obtained using a portion of each of a pair of sand molds 8. In the casting process, as shown in Figure 6(a), multiple sand molds 8 are arranged in a straight line in a predetermined direction. Then, as shown in Figure 6(b), a pair of sand molds 8 arranged in the direction of alignment are combined such that the convex portion 81 of one sand mold 8 fits into the concave portion 82 of the other sand mold 8, and molten metal 90 is poured into the space 800 formed between the outer surface of the convex portion 81 and the inner surface of the concave portion 82. In Figure 6(b), the molten metal 90 poured into the space 800 is shown in dark gray. After the molten metal 90 has solidified, as shown in Figure 6(c), the sand molds 8 are broken apart and the casting 9 is removed.

[0040] In the cutting process, the casting 9 is machined to form the inner surfaces 211a and 212a of the first and second housing portions 211 and 212 of the housing hole 210, the bolt insertion holes 220 of the flange portion 22, the oil grooves 241 of the boss portion 24, and the mating surface 2a with the lid member 5. However, the inner surfaces 20a and 20b of the oil hole 20 and the bottom surface 20c do not require high precision, so machining is not necessary for them.

[0041] (Effects of the embodiment) According to the embodiment of the present invention described above, the oil holes 20 of the differential case 2 can be formed by casting, making it easier to process the differential case 2. Furthermore, since a casting 9 can be obtained using a pair of sand molds 8 as a mold, the structure of the mold is simplified compared to when three or more sand molds are combined. Moreover, since the circumferential width W of the oil holes 20 of the differential case 2 is formed so that it does not narrow from one end 201 to the other end 202 of the oil holes 20, the protrusions 83 of the sand mold 8 for forming the oil holes 20 can be easily formed by the slide mold 73. Thus, according to this embodiment, it is possible to improve the mass production of the differential case 2, and consequently, to reduce the cost of the differential 1.

[0042] (Note) The present invention has been described above based on embodiments, but these embodiments do not limit the invention as defined in the claims. It should also be noted that not all combinations of features described in the embodiments are necessarily essential for solving the problem of the invention. Furthermore, the present invention can be modified as appropriate by omitting some components, or by adding or substituting components, without departing from its spirit, and can be modified as follows, for example.

[0043] In the above embodiment, the case in which lubricating oil is supplied to the differential gear 1 as oil droplets 100 from above in the vertical direction was described, but it is not limited to this, and for example, the differential gear 1 may be positioned so that a part of the differential case 2 is immersed in lubricating oil, and lubricating oil may be supplied into the differential case 2 from the oil hole 20 by the scraping caused by the rotation of the differential case 2. Also, although Figure 1 shows the case in which the ring gear 13 is a bevel gear, it is not limited to this, and the ring gear 13 may be a spur gear. [Explanation of Symbols]

[0044] 1... Differential gear 2... Differential case 20c...Bottom surface 21...Cylindrical section 210...Accommodation opening 211...First accommodation section 212...Second containment section 213...Sectional partition wall 22...Flange section 23...Bottom section 23a...Outer surface 31...First side gear 32...Second side gear 4...Pinion gear assembly 41...First pinion gear 42...Second pinion gear Da...Minimum distance Db...Tip circle diameter O... Axis of rotation W... Circumferential width

Claims

1. The differential includes a differential case that rotates in response to the driving force of a drive source, a first side gear and a second side gear coaxially arranged within the differential case along the rotation axis of the differential case, and a plurality of pinion gear sets formed by meshing a first pinion gear that meshes with the first side gear and a second pinion gear that meshes with the second side gear. The differential case integrally comprises a cylindrical portion having a plurality of housing holes for housing each of the plurality of pinion gear sets, a flange portion provided on the outer circumference of one end of the cylindrical portion, and a bottom portion provided on the inside of the other end of the cylindrical portion. An oil hole for introducing lubricating oil into the differential case is formed in the differential case, extending in the axial direction along the axis of rotation. The oil hole has one end in the axial direction formed in the cylindrical portion, and the other end in the axial direction is open to the outer surface at the bottom. The width of the oil holes in the circumferential direction of the cylindrical portion is formed so that it does not narrow from one end to the other end. The minimum distance between the inner surface of the oil hole at the bottom and the axis of rotation is shorter than half the diameter of the tip circle of the first side gear. Differential device.

2. The pinion gear set comprises two second pinion gears meshing with one first pinion gear. The second pinion gear is shorter than the first pinion gear and is positioned so as to be offset towards the flange portion rather than the bottom portion in the axial direction. The housing hole has a first housing portion for housing the first pinion gear and two second housing portions for housing the two second pinion gears, and the second housing portions are formed on both sides of the first housing portion in the circumferential direction of the cylindrical portion. The oil holes are aligned in the axial direction with the partition wall separating the second housing portions of a pair of adjacent housing holes in the circumferential direction of the cylindrical portion, and are formed between the first housing portions of the pair of housing holes. The differential device according to claim 1.

3. Of the pair of inner surfaces of the oil holes facing each other in the circumferential direction of the cylindrical portion, one inner surface facing the front side in the main rotation direction of the differential case is concave, and the other inner surface facing the rear side in the main rotation direction of the differential case is convex. The differential device according to claim 1 or 2.

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